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Transformation between oxidation states is widespread in transition metal coordination chemistry and biochemistry, typically occurring in solution. However, air-induced oxidation in porous crystalline solids with retention of crystallinity is rare due to the dearth of materials with high structural stability that are inherently redox active. Herein, we report a new family of such materials, four isostructural cobalt-pyrazolate frameworks of face-centered cubic, fcu , topology, fcu-L-Co , that are sustained by Co 8 molecular building blocks (MBBs) and dipyrazolate ligands, L . fcu-L-Co were observed to spontaneously transform from Co(II) 8 to Co(III) 8 MBBs in air with retention of crystallinity, marking the first such instance in metal-organic frameworks (MOFs). This transformation can also be achieved through water vapor sorption cycling, heating, or chemical oxidation. The reverse reactions were conducted by exposure of fcu-L-Co(III) to aqueous hydrazine. fcu-L-Co(II) exhibited high gravimetric water vapor uptakes of 0.55-0.68 g g -1 at 30% relative humidity (RH), while in fcu-L-Co(III) the inflection point shifted to lower RH and framework stability improved. Insight into the transformation between fcu-L-Co(II) and fcu-L-Co(III) was gained from single crystal X-ray diffraction and in situ spectroscopy. Overall, the crystal engineering approach we adopted has afforded a new family of MOFs that exhibit cobalt redox chemistry in a confined space coupled with high porosity.

We report a crystal-engineering study conducted upon a platform of three mixed-linker square lattice ( sql ) coordination networks of general formula [Zn(Ria)(bphy)] [bphy = 1,2-bis(pyridin-4-yl)hydrazine, H 2 Ria = 5-position-substituted isophthalic acid, and R = -Br, -NO 2 , and -OH; compounds 1 - 3 ]. Analysis of single-crystal X-ray diffraction data of 1 - 2 and the simulated crystal structure of 3 revealed that 1 - 3 are isomorphous and sustained by bilayers of sql networks linked by hydrogen bonds. Although similar pore shapes and sizes exist in 1 - 3 , distinct isotherm shapes (linear and S shape) and uptakes (2.4, 11.6, and 13.3 wt %, respectively) were observed. Ab initio calculations indicated that the distinct water sorption properties can be attributed to the R groups, which offer a range of hydrophilicity. Calculations indicated that the significantly lower experimental uptake in compound 1 can be attributed to a constricted channel. The calculated water-binding sites provide insights into how adsorbed water molecules bond to the pore walls, with the strongest interactions, water-hydroxyl hydrogen bonding, observed for 3 . Overall, this study reveals how pore engineering can result in large variations in water sorption properties in an isomorphous family of rigid porous coordination networks.

The stimulus-responsive behavior of coordination networks (CNs), which switch between closed (nonporous) and open (porous) phases, is of interest because of its potential utility in gas storage and separation. Herein, we report two polymorphs of a new square-lattice ( sql ) topology CN, X-sql-1-Cu , of formula [Cu(Imibz) 2 ] n (HImibz = {[4-(1 H -imidazol-1-yl)phenylimino]methyl}benzoic acid), isolated from the as-synthesized CN X-sql-1-Cu-(MeOH) 2 ·2MeOH , which subsequently transformed to a narrow pore solvate, X-sql-1-Cu-A·MeOH , upon mild activation (drying in air or heating at 333 K under nitrogen). X-sql-1-Cu-A·MeOH contains MeOH in cavities, which was removed through exposure to vacuum for 2 h, yielding the nonporous (closed) phase X-sql-1-Cu-A . In contrast, a more dense polymorph, X-sql-1-Cu-B , was obtained by exposing X-sql-1-Cu-(MeOH) 2 ·2MeOH directly to vacuum for 2 h. Gas sorption studies conducted on X-sql-1-Cu-A and X-sql-1-Cu-B revealed different switching behaviors to two open phases ( X-sql-1-Cu·CO 2 and X-sql-1-Cu·C 2 H 2 ), with different gate-opening threshold pressures for CO 2 at 195 K and C 2 H 2 at 278 K. Coincident CO 2 sorption and in situ powder X-ray diffraction studies at 195 K revealed that X-sql-1-Cu-A transformed to X-sql-1-Cu-B after the first sorption cycle and that the CO 2 -induced switching transformation was thereafter reversible. The results presented herein provide insights into the relationship between two polymorphs of a CN and the effect of polymorphism upon gas sorption properties. To the best of our knowledge, whereas sql networks such as X-sql-1-Cu are widely studied in terms of their structural and sorption properties, this study represents only the second example of an in-depth study of the sorption properties of polymorphic sql networks.

Porous coordination networks (PCNs) sustained by inorganic anions that serve as linker ligands can offer high selectivity toward specific gases or vapors in gas mixtures. Such inorganic anions are best exemplified by electron-rich fluorinated anions, e.g., SiF 6 2- , TiF 6 2- , and NbOF 5 2- , although sulfate anions have recently been highlighted as inexpensive and earth-friendly alternatives. Herein, we report the use of a rare copper sulfate dimer molecular building block to generate two square lattice, sql , coordination networks which can be prepared via solvent layering or slurrying, CuSO 4 (1,4-bib) 1.5 , 1 , (1,4-bib = 1,4-bisimidazole benzene) and CuSO 4 (1,4-bin) 1.5 , 2 , (1,4-bin = 1,4-bisimidazole naphthalene). Variable-temperature SCXRD and PXRD experiments revealed that both sql networks underwent reversible structural transformations due to linker rotations or internetwork displacements. Gas sorption studies conducted upon the narrow-pore phase of CuSO 4 (1,4-bin) 1.5 , 2np , found a high calculated 1:99 selectivity for C 2 H 2 over C 2 H 4 (33.01) and CO 2 (15.18), as well as strong breakthrough performance. Across-the-board, C 3 H 4 selectivity vs C 3 H 6 , CO 2 , and C 3 H 8 was also observed. Sulfate-based PCNs, although still understudied, appear increasingly likely to offer utility in gas and vapor separations., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

High and increasing production of separation of C8 aromatic isomers demands the development of purification methods that are efficient, scalable, and inexpensive, especially for p -xylene, PX, the largest volume C8 commodity. Herein, we report that 4-(1 H -1,2,4-triazol-1-yl)-phenyl-1 H -benzo[de]isoquinoline-1,3(2H)-dione ( TPBD ), a molecular compound that can be prepared and scaled up via solid-state synthesis, exhibits exceptional PX selectivity over each of the other C8 isomers, o -xylene (OX), m -xylene (MX), and ethylbenzene (EB). The apohost or α form of TPBD was found to exhibit conformational polymorphism in the solid state enabled by rotation of its triazole and benzene rings. TPBD-αI and TPBD-αII are nonporous polymorphs that transformed to the same PX inclusion compound, TPBD-PX , upon contact with liquid PX. TPBD enabled highly selective capture of PX, as established by competitive slurry experiments involving various molar ratios in binary, ternary, and quaternary mixtures of C8 aromatics. Binary selectivity values for PX as determined by 1 H NMR spectroscopy and gas chromatography ranged from 22.4 to 108.4, setting new benchmarks for both PX/MX (70.3) and PX/EB (59.9) selectivity as well as close to benchmark selectivity for PX/OX (108.4). To our knowledge, TPBD is the first material of any class to exhibit such high across-the-board PX selectivity from quaternary mixtures of C8 aromatics under ambient conditions. Crystallographic and computational studies provide structural insight into the PX binding site in TPBD-PX , whereas thermal stability and capture kinetics were determined by variable-temperature powder X-ray diffraction and slurry tests, respectively. That TPBD offers benchmark PX selectivity and facile recyclability makes it a prototypal molecular compound for PX purification or capture under ambient conditions.

Separation of the C 8 aromatic isomers, xylenes (PX, MX, and OX) and ethylbenzene (EB), is important to the petrochemical industry. Whereas physisorptive separation is an energy-efficient alternative to current processes, such as distillation, physisorbents do not generally exhibit strong C 8 selectivity. Herein, we report the mixed-linker square lattice ( sql ) coordination network [Zn 2 (sba) 2 (bis)] n · m DMF ( sql-4,5-Zn , H 2 sba or 4 = 4,4'-sulfonyldibenzoic acid, bis or 5 = trans-4,4'-bis(1-imidazolyl)stilbene) and its C 8 sorption properties. sql-4,5-Zn was found to exhibit high uptake capacity for liquid C 8 aromatics (∼20.2 wt %), and to the best of our knowledge, it is the first sorbent to exhibit selectivity for PX, EB, and MX over OX for binary, ternary, and quaternary mixtures from gas chromatography. Single-crystal structures of narrow-pore, intermediate-pore, and large-pore phases provided insight into the phase transformations, which were enabled by flexibility of the linker ligands and changes in the square grid geometry and interlayer distances. This work adds to the library of two-dimensional coordination networks that exhibit high uptake, thanks to clay-like expansion, and strong selectivity, thanks to shape-selective binding sites, for C 8 isomers., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Herein, we introduce a new square lattice topology coordination network, sql-(1,3-bib)(ndc)-Ni, with three types of connection and detail its gas and vapour induced phase transformations. Exposure to humidity resulted in an S-shaped isotherm profile, suggesting potential utility of such materials as desiccants.

Chiral metal-organic materials, CMOMs, are of interest as they can offer selective binding sites for chiral guests. Such binding sites can enable CMOMs to serve as chiral crystalline sponges (CCSs) to determine molecular structure and/or purify enantiomers. We recently reported on the chiral recognition properties of a homochiral cationic diamondoid, dia, network {[Ni( S -IDEC)(bipy)(H 2 O)][NO 3 ]} n ( S -IDEC = S -indoline-2-carboxylicate, bipy = 4,4'-bipyridine), CMOM-5[NO 3 ] . The modularity of CMOM-5[NO 3 ] means there are five feasible approaches to fine-tune structures and properties via substitution of one or more of the following components: metal cation (Ni 2+ ); bridging ligand ( S -IDEC); linker (bipy); extra-framework anion (NO 3 - ); and terminal ligand (H 2 O). Herein, we report the effect of anion substitution on the CCS properties of CMOM-5[NO 3 ] by preparing and characterizing {[Ni( S -IDEC)(bipy)(H 2 O)][BF 4 ]} n , CMOM-5[BF 4 ] . The chiral channels in CMOM-5[BF 4 ] enabled it to function as a CCS for determination of the absolute crystal structures of both enantiomers of three chiral compounds: 1-phenyl-1-butanol (1P1B); methyl mandelate (MM); ethyl mandelate (EM). Chiral resolution experiments revealed CMOM-5[BF 4 ] to be highly selective toward the S -isomers of MM and EM with enantiomeric excess, ee, values of 82.6 and 78.4%, respectively. The ee measured for S -EM surpasses the 64.3% exhibited by [DyNaL(H 2 O) 4 ] 6H 2 O and far exceeds that of CMOM-5[NO 3 ] (6.0%). Structural studies of the binding sites in CMOM-5[BF 4 ] provide insight into their high enantioselectivity., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Bifunctional N-donor carboxylate linkers generally afford dia and sql topology coordination networks of general formula ML 2 that are based upon the MN 2 (CO 2 ) 2 molecular building block (MBB). Herein, we report on a new N-donor carboxylate linker, β-(3,4-pyridinedicarboximido)propionate (PyImPr), which afforded Cd(PyImPr) 2 via reaction of PyImPrH with Cd(acetate) 2 ·2H 2 O. We observed that, depending upon whether Cd(PyImPr) 2 was prepared by layering or solvothermal methods, 2D or 3D supramolecular isomers, respectively, of Cd(PyImPr) 2 were isolated. Single crystal X-ray diffraction studies revealed that both supramolecular isomers are comprised of the same carboxylate bridged rod building block, RBB. We were interested to determine if the ethylene moiety of PyImPr could enable structural flexibility. Indeed, open-to-closed structural transformations occurred upon solvent removal for both phases, but they were found to be irreversible. A survey of the Cambridge Structural Database (CSD) was conducted to analyse the relative frequency of RBB topologies in related ML 2 coordination networks in order to provide insight from a crystal engineering perspective., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Ultramicroporous materials can be highly effective at trace gas separations when they offer a high density of selective binding sites. Herein, we report that sql-NbOFFIVE-bpe-Cu , a new variant of a previously reported ultramicroporous square lattice, sql , topology material, sql-SIFSIX-bpe-Zn , can exist in two polymorphs. These polymorphs, sql-NbOFFIVE-bpe-Cu-AA ( AA ) and sql-NbOFFIVE-bpe-Cu-AB ( AB ), exhibit AAAA and ABAB packing of the sql layers, respectively. Whereas NbOFFIVE-bpe-Cu-AA ( AA ) is isostructural with sql-SIFSIX-bpe-Zn , each exhibiting intrinsic 1D channels, sql-NbOFFIVE-bpe-Cu-AB ( AB ) has two types of channels, the intrinsic channels and extrinsic channels between the sql networks. Gas and temperature induced transformations of the two polymorphs of sql-NbOFFIVE-bpe-Cu were investigated by pure gas sorption, single-crystal X-ray diffraction (SCXRD), variable temperature powder X-ray diffraction (VT-PXRD), and synchrotron PXRD. We observed that the extrinsic pore structure of AB resulted in properties with potential for selective C 3 H 4 /C 3 H 6 separation. Subsequent dynamic gas breakthrough measurements revealed exceptional experimental C 3 H 4 /C 3 H 6 selectivity (270) and a new benchmark for productivity (118 mmol g -1 ) of polymer grade C 3 H 6 (purity > 99.99%) from a 1:99 C 3 H 4 /C 3 H 6 mixture. Structural analysis, gas sorption studies, and gas adsorption kinetics enabled us to determine that a binding "sweet spot" for C 3 H 4 in the extrinsic pores is behind the benchmark separation performance. Density-functional theory (DFT) calculations and Canonical Monte Carlo (CMC) simulations provided further insight into the binding sites of C 3 H 4 and C 3 H 6 molecules within these two hybrid ultramicroporous materials, HUMs. These results highlight, to our knowledge for the first time, how pore engineering through the study of packing polymorphism in layered materials can dramatically change the separation performance of a physisorbent.

Chiral metal-organic materials (CMOMs), can offer molecular binding sites that mimic the enantioselectivity exhibited by biomolecules and are amenable to systematic fine-tuning of structure and properties. Herein, we report that the reaction of Ni(NO 3 ) 2 , S -indoline-2-carboxylic acid ( S -IDECH), and 4,4'-bipyridine (bipy) afforded a homochiral cationic diamondoid, dia , network, [Ni( S -IDEC)(bipy)(H 2 O)][NO 3 ], CMOM-5 . Composed of rod building blocks (RBBs) cross-linked by bipy linkers, the activated form of CMOM-5 adapted its pore structure to bind four guest molecules, 1-phenyl-1-butanol (1P1B), 4-phenyl-2-butanol (4P2B), 1-(4-methoxyphenyl)ethanol (MPE), and methyl mandelate (MM), making it an example of a chiral crystalline sponge (CCS). Chiral resolution experiments revealed enantiomeric excess, ee , values of 36.2-93.5%. The structural adaptability of CMOM-5 enabled eight enantiomer@ CMOM-5 crystal structures to be determined. The five ordered crystal structures revealed that host-guest hydrogen-bonding interactions are behind the observed enantioselectivity, three of which represent the first crystal structures determined of the ambient liquids R -4P2B, S-4P2B, and R -MPE., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Coordination networks (CNs) that undergo gas-induced transformation from closed (nonporous) to open (porous) structures are of potential utility in gas storage applications, but their development is hindered by limited control over their switching mechanisms and pressures. In this work, we report two CNs, [Co(bimpy)(bdc)] n ( X-dia-4-Co ) and [Co(bimbz)(bdc)] n ( X-dia-5-Co ) (H 2 bdc = 1,4-benzendicarboxylic acid; bimpy = 2,5-bis(1H-imidazole-1-yl)pyridine; bimbz = 1,4-bis(1H-imidazole-1-yl)benzene), that both undergo transformation from closed to isostructural open phases involving at least a 27% increase in cell volume. Although X-dia-4-Co and X-dia-5-Co only differ from one another by one atom in their N -donor linkers (bimpy = pyridine, and bimbz = benzene), this results in different pore chemistry and switching mechanisms. Specifically, X-dia-4-Co exhibited a gradual phase transformation with a steady increase in the uptake when exposed to CO 2 , whereas X-dia-5-Co exhibited a sharp step (type F-IV isotherm) at P / P 0 ≈ 0.008 or P ≈ 3 bar (195 or 298 K, respectively). Single-crystal X-ray diffraction, in situ powder XRD, in situ IR, and modeling (density functional theory calculations, and canonical Monte Carlo simulations) studies provide insights into the nature of the switching mechanisms and enable attribution of pronounced differences in sorption properties to the changed pore chemistry.

In this work, we present the first metal-organic framework (MOF) platform with a self-penetrated double diamondoid ( ddi ) topology that exhibits switching between closed (nonporous) and open (porous) phases induced by exposure to gases. A crystal engineering strategy, linker ligand substitution, was used to control gas sorption properties for CO 2 and C3 gases. Specifically, bimbz (1,4-bis(imidazol-1-yl)benzene) in the coordination network X-ddi-1-Ni ([Ni 2 (bimbz) 2 (bdc) 2 (H 2 O)] n , H 2 bdc = 1,4-benzenedicarboxylic acid) was replaced by bimpz (3,6-bis(imidazol-1-yl)pyridazine) in X-ddi-2-Ni ([Ni 2 (bimpz) 2 (bdc) 2 (H 2 O)] n ). In addition, the 1:1 mixed crystal X-ddi-1,2-Ni ([Ni 2 (bimbz)(bimpz)(bdc) 2 (H 2 O)] n ) was prepared and studied. All three variants form isostructural closed ( β ) phases upon activation which each exhibited different reversible properties upon exposure to CO 2 at 195 K and C3 gases at 273 K. For CO 2 , X-ddi-1-Ni revealed incomplete gate-opening, X-ddi-2-Ni exhibited a stepped isotherm with saturation uptake of 3.92 mol·mol -1 , and X-ddi-1,2-Ni achieved up to 62% more gas uptake and a distinct isotherm shape vs the parent materials. Single-crystal X-ray diffraction (SCXRD) and in situ powder X-ray diffraction (PXRD) experiments provided insight into the mechanisms of phase transformation and revealed that the β phases are nonporous with unit cell volumes 39.9, 40.8, and 41.0% lower than the corresponding as-synthesized α phases, X-ddi-1-Ni-α , X-ddi-2-Ni-α , and X-ddi-1,2-Ni-α , respectively. The results presented herein represent the first report of reversible switching between closed and open phases in ddi topology coordination networks and further highlight how ligand substitution can profoundly impact the gas sorption properties of switching sorbents., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

In this work, we report the synthesis, structural characterisation and sorption properties of an 8-fold interpenetrated diamondoid (dia) metal-organic framework (MOF) that is sustained by a new extended linker ligand, [Cd(Imibz) 2 ], X-dia-2-Cd, HImibz or 2 = 4-((4-(1 H -imidazol-1-yl)phenylimino)methyl)benzoic acid. X-dia-2-Cd was found to exhibit reversible single-crystal-to-single-crystal (SC-SC) transformations between four distinct phases: an as-synthesised (from N , N -dimethylformamide) wide-pore phase, X-dia-2-Cd-α; a narrow-pore phase, X-dia-2-Cd-β, formed upon exposure to water; a narrow-pore phase obtained by activation, X-dia-2-Cd-γ; a medium-pore CO 2 -loaded phase X-dia-2-Cd-δ. While the space group remained constant in the four phases, the cell volumes and calculated void space ranged from 4988.7 Å 3 and 47% (X-dia-2-Cd-α), respectively, to 3200.8 Å 3 and 9.1% (X-dia-2-Cd-γ), respectively. X-dia-2-Cd-γ also exhibited a water vapour-induced structural transformation to the water-loaded X-dia-2-Cd-β phase, resulting in an S-shaped sorption isotherm. The inflection point occurred at 18% RH with negligible hysteresis on the desorption profile. Water vapour temperature-humidity swing cycling (60% RH, 300 K to 0% RH, 333 K) indicated hydrolytic stability of X-dia-2-Cd and working capacity was retained after 128 cycles of sorbent regeneration. CO 2 (at 195 K) was also observed to induce a structural transformation in X-dia-2-Cd-γ and in situ PXRD studies at 1 bar of CO 2 , 195 K revealed the formation of X-dia-2-Cd-δ, which exhibited 31% larger unit cell volume than X-dia-2-Cd-γ., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A molecular porous material, MPM-2, comprised of cationic [Ni 2 (AlF 6 )(pzH) 8 (H 2 O) 2 ] and anionic [Ni 2 Al 2 F 11 (pzH) 8 (H 2 O) 2 ] complexes that generate a charge-assisted hydrogen-bonded network with pcu topology is reported. The packing in MPM-2 is sustained by multiple interionic hydrogen bonding interactions that afford ultramicroporous channels between dense layers of anionic units. MPM-2 is found to exhibit excellent stability in water (>1 year). Unlike most hydrogen-bonded organic frameworks which typically show poor stability in organic solvents, MPM-2 exhibited excellent stability with respect to various organic solvents for at least two days. MPM-2 is found to be permanently porous with gas sorption isotherms at 298 K revealing a strong affinity for C 2 H 2 over CO 2 thanks to a high (ΔQ st ) AC [Q st (C 2 H 2 ) - Q st (CO 2 )] of 13.7 kJ mol -1 at low coverage. Dynamic column breakthrough experiments on MPM-2 demonstrated the separation of C 2 H 2 from a 1:1 C 2 H 2 /CO 2 mixture at 298 K with effluent CO 2 purity of 99.995% and C 2 H 2 purity of >95% after temperature-programmed desorption. C-H···F interactions between C 2 H 2 molecules and F atoms of AlF 6 3- are found to enable high selectivity toward C 2 H 2 , as determined by density functional theory simulations., (© 2022 The Authors. Small published by Wiley-VCH GmbH.)

Herein, we report the crystal structure and guest binding properties of a new two-dimensional (2D) square lattice ( sql ) topology coordination network, sql-(azpy)(pdia)-Ni , which is comprised of two linker ligands with diazene (azo) moieties, ( E )-1,2-di(pyridin-4-yl)diazene(azpy) and ( E )-5-(phenyldiazenyl)isophthallate(pdia). sql-(azpy)(pdia)-Ni underwent guest-induced switching between a closed (nonporous) β phase and several open (porous) α phases, but unlike the clay-like layer expansion to distinct phases previously reported in switching sql networks, a continuum of phases was formed. In effect, sql-(azpy)(pdia)-Ni exhibited elastic-like properties induced by adaptive guest binding. Single-crystal X-ray diffraction (SCXRD) studies of the α phases revealed that the structural transformations were enabled by the pendant phenyldiazenyl moiety on the pdia 2- ligand. This moiety functioned as a type of hinge to enable parallel slippage of layers and interlayer expansion for the following guests: N , N -dimethylformamide, water, dichloromethane, para -xylene, and ethylbenzene. The slippage angle (interplanar distances) ranged from 54.133° (4.442 Å) in the β phase to 69.497° (5.492 Å) in the ethylbenzene-included phase. Insight into the accompanying phase transformations was also gained from variable temperature powder XRD studies. Dynamic water vapor sorption studies revealed a stepped isotherm with little hysteresis that was reversible for at least 100 cycles. The isotherm step occurred at ca. 50% relative humidity (RH), the optimal RH value for humidity control., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

That physisorbents can reduce the energy footprint of water vapor capture and release has attracted interest because of potential applications such as moisture harvesting, dehumidification, and heat pumps. In this context, sorbents exhibiting an S-shaped single-step water sorption isotherm are desirable, most of which are structurally rigid sorbents that undergo pore-filling at low relative humidity (RH), ideally below 30% RH. Here, we report that a new flexible one-dimensional (1D) coordination network, [Cu(HQS)(TMBP)] (H 2 HQS = 8-hydroxyquinoline-5-sulfonic acid and TMBP = 4,4'-trimethylenedipyridine), exhibits at least five phases: two as-synthesized open phases, α ⊃ H 2 O and β ⊃ MeOH; an activated closed phase (γ); CO 2 (δ ⊃ CO 2 ) and C 2 H 2 (ϵ ⊃ C 2 H 2 ) loaded phases. The γ phase underwent a reversible structural transformation to α ⊃ H 2 O with a stepped sorption profile (Type F-IV) when exposed to water vapor at <30% RH at 300 K. The hydrolytic stability of [Cu(HQS)(TMBP)] was confirmed by powder X-ray diffraction (PXRD) after immersion in boiling water for 6 months. Temperature-humidity swing cycling measurements demonstrated that working capacity is retained for >100 cycles and only mild heating (<323 K) is required for regeneration. Unexpectedly, the kinetics of loading and unloading of [Cu(HQS)(TMBP)] compares favorably with well-studied rigid water sorbents such as Al-fumarate, MOF-303, and CAU-10-H. Furthermore, a polymer composite of [Cu(HQS)(TMBP)] was prepared and its water sorption retained its stepped profile and uptake capacity over multiple cycles.

Although pyrazine-linked hybrid ultramicroporous materials (HUMs, pore size <7 Å) are benchmark physisorbents for trace carbon dioxide (CO 2 ) capture under dry conditions, their affinity for water (H 2 O) mitigates their carbon capture performance in humid conditions. Herein, we report on the co-adsorption of H 2 O and CO 2 by TIFSIX-3-Ni-a high CO 2 affinity HUM-and find that slow H 2 O sorption kinetics can enable CO 2 uptake and release using shortened adsorption cycles with retention of ca. 90 % of dry CO 2 uptake. Insight into co-adsorption is provided by in situ infrared spectroscopy and ab initio calculations. The binding sites and sorption mechanisms reveal that both CO 2 and H 2 O molecules occupy the same ultramicropore through favorable interactions between CO 2 and H 2 O at low water loading. An energetically favored water network displaces CO 2 molecules at higher loading. Our results offer bottom-up design principles and insight into co-adsorption of CO 2 and H 2 O that is likely to be relevant across the full spectrum of carbon capture sorbents to better understand and address the challenge posed by humidity to gas capture., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Gas separation performances are usually degraded under humid conditions for many crystalline porous materials because of the lack of water stability and/or the competition of water vapor toward the interaction sites (e.g., open metal sites). Zeolitic imidazolate frameworks (ZIFs) are suitable candidates for practical applications in gas separation because of their excellent physical/chemical stabilities. However, the limitation of substituent positions in common ZIFs has prevented extensive pore engineering to improve their separation performance. In a type of gyroidal ZIFs with gie topology, the Schiff base moiety provides additional substituent positions, making it possible to modify the spatial arrangement of hydrophobic methyl groups. Herein, a new gyroidal ZIF, ZnBAIm (H 2 BAIm = 1,2-bis(1-(1 H -imidazol-4-yl)ethylidene)hydrazine), is designed, synthesized, and characterized. The spatially modified ZnBAIm exhibits improved thermal/chemical/mechanical stabilities compared to ZnBIm (H 2 BIm = 1,2-bis((5 H -imidazol-4-yl)methylene)hydrazine). ZnBAIm can remain intact up to about 480 °C in a N 2 atmosphere and tolerate harsh treatments (e.g., 5 M NaOH aqueous solution at room temperature for 24 h and 190 MPa high pressure in the presence of water). Moreover, the modified pore and window sizes have improved significantly the ethane/ethylene selectivity and separation performance under humid conditions for ZnBAIm. Breakthrough experiments demonstrate efficient separation of a C 2 H 6 /C 2 H 4 (50/50, v/v) binary gas mixture under ambient conditions; more importantly, the C 2 H 6 /C 2 H 4 separation performance is unaffected under highly humid conditions (up to 80% RH). The separation performance is attributed to combined thermodynamic (stronger dispersion interaction with C 2 H 6 than with C 2 H 4 ) and kinetic factors (diffusion), determined by density functional theory calculations and kinetic adsorption study, respectively.

Hybrid ultramicroporous materials, HUMs, are comprised of metal cations linked by combinations of inorganic and organic ligands. Their modular nature makes them amenable to crystal engineering studies, which have thus far afforded four HUM platforms (as classified by the inorganic linkers). HUMs are of practical interest because of their benchmark gas separation performance for several industrial gas mixtures. We report herein design and gram-scale synthesis of the prototypal sulfate-linked HUM, the fsc topology coordination network ([Zn(tepb)(SO 4 )] n ), SOFOUR-1-Zn, tepb=(tetra(4-pyridyl)benzene). Alignment of the sulfate anions enables strong binding to C 2 H 2 via O⋅⋅⋅HC interactions but weak CO 2 binding, affording a new benchmark for the difference between C 2 H 2 and CO 2 heats of sorption at low loading (ΔQ st =24 kJ mol -1 ). Dynamic column breakthrough studies afforded fuel-grade C 2 H 2 from trace (1 : 99) or 1 : 1 C 2 H 2 /CO 2 mixtures, outperforming its SiF 6 2- analogue, SIFSIX-22-Zn., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The trade-off between selectivity and adsorption capacity with porous materials is a major roadblock to reducing the energy footprint of gas separation technologies. To address this matter, we report herein a systematic crystal engineering study of C 2 H 2 removal from CO 2 in a family of hybrid ultramicroporous materials (HUMs). The HUMs are composed of the same organic linker ligand, 4-(3,5-dimethyl-1 H -pyrazol-4-yl)pyridine, pypz, three inorganic pillar ligands, and two metal cations, thereby affording six isostructural pcu topology HUMs. All six HUMs exhibited strong binding sites for C 2 H 2 and weaker affinity for CO 2 . The tuning of pore size and chemistry enabled by crystal engineering resulted in benchmark C 2 H 2 /CO 2 separation performance. Fixed-bed dynamic column breakthrough experiments for an equimolar (v/v = 1:1) C 2 H 2 /CO 2 binary gas mixture revealed that one sorbent, SIFSIX-21-Ni, was the first C 2 H 2 selective sorbent that combines exceptional separation selectivity (27.7) with high adsorption capacity (4 mmol·g -1 )., Competing Interests: The authors declare no competing interests., (© 2021 The Authors.)

Pyrazine-linked hybrid ultramicroporous (pore size <7 Å) materials (HUMs) offer benchmark performance for trace carbon capture thanks to strong selectivity for CO 2 over small gas molecules, including light hydrocarbons. That the prototypal pyrazine-linked HUMs are amenable to crystal engineering has enabled second generation HUMs to supersede the performance of the parent HUM, SIFSIX-3-Zn, mainly through substitution of the metal and/or the inorganic pillar. Herein, we report that two isostructural aminopyrazine-linked HUMs, MFSIX-17-Ni (17=aminopyrazine; M=Si, Ti), which we had anticipated would offer even stronger affinity for CO 2 than their pyrazine analogs, unexpectedly exhibit reduced CO 2 affinity but enhanced C 2 H 2 affinity. MFSIX-17-Ni are consequently the first physisorbents that enable single-step production of polymer-grade ethylene (>99.95 % for SIFSIX-17-Ni) from a ternary equimolar mixture of ethylene, acetylene and CO 2 thanks to coadsorption of the latter two gases. We attribute this performance to the very different binding sites in MFSIX-17-Ni versus SIFSIX-3-Zn., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The high energy footprint of commodity gas purification and increasing demand for gases require new approaches to gas separation. Kinetic separation of gas mixtures through molecular sieving can enable separation by molecular size or shape exclusion. Physisorbents must exhibit the right pore diameter to enable separation, but the 0.3-0.4 nm range relevant to small gas molecules is hard to control. Herein, dehydration of the ultramicroporous metal-organic framework Ca-trimesate, Ca(HBTC)⋅H 2 O (H 3 BTC=trimesic acid), bnn-1-Ca-H 2 O, affords a narrow pore variant, Ca(HBTC), bnn-1-Ca. Whereas bnn-1-Ca-H 2 O (pore diameter 0.34 nm) exhibits ultra-high CO 2 /N 2 , CO 2 /CH 4 , and C 2 H 2 /C 2 H 4 binary selectivity, bnn-1-Ca (pore diameter 0.31 nm) offers ideal selectivity for H 2 /CO 2 and H 2 /N 2 under cryogenic conditions. Ca-trimesate, the first physisorbent to exhibit H 2 sieving under cryogenic conditions, could be a prototype for a general approach to exert precise control over pore diameter in physisorbents., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Separation of the C8 aromatic isomers, p -xylene (PX), m -xylene (MX), o -xylene (OX) and ethylbenzene (EB), is relevant thanks to their widespread application as chemical feedstocks but challenging because of their similar boiling points and close molecular dimensions. Physisorptive separation could offer an energy-efficient solution to this challenge but sorbents which exhibit strong selectivity for one of the isomers remain a largely unmet challenge despite recent reports of OX or PX selective sorbents with high uptake capacity. For example, the square lattice, sql , topology coordination network [Co(bipy) 2 (NCS) 2 ] n (sql-1-Co-NCS) exhibits the rare combination of high OX selectivity and high uptake capacity. Herein we report that a crystal engineering approach enabled isolation of the mixed-linker sql coordination network [Co(bipy)(bptz)(NCS) 2 ] n ( sql-1,3-Co-NCS , bipy = 4,4'-bipyridine, bptz = 4,4'-bis(4-pyridyl)tetrazine) and study of its C8 vapour and liquid sorption properties. sql-1,3-Co-NCS was found to exhibit high adsorption capacity from liquid xylenes (∼37 wt%) and is to our knowledge the first sorbent to exhibit high selectivity for each of xylene isomer over EB ( S OX/EB , S MX/EB , S PX/EB > 5). Insights into the performance of sql-1,3-Co-NCS are gained from structural studies which reveal stacking interactions between electron-deficient bptz linkers and the respective xylenes. sql-1,3-Co-NCS is the first N-donor mixed-linker sql coordination network studied for its gas/vapour sorption properties and represents a large and diverse class of understudied coordination networks., (This journal is © The Royal Society of Chemistry 2020.)

Acetylene (C 2 H 2 ) capture is a step in a number of industrial processes, but it comes with a high-energy footprint. Although physisorbents have the potential to reduce this energy footprint, they are handicapped by generally poor selectivity versus other relevant gases, such as CO 2 and C 2 H 4 . In the case of CO 2 , the respective physicochemical properties are so similar that traditional physisorbents, such as zeolites, silica, and activated carbons cannot differentiate well between CO 2 and C 2 H 2 . Herein, we report that a family of three isostructural, ultramicroporous (<7 Å) diamondoid metal-organic frameworks, [Cu(TMBP)X] (TMBP=3,3',5,5'-tetramethyl-4,4'-bipyrazole), TCuX (X=Cl, Br, I), offer new benchmark C 2 H 2 /CO 2 separation selectivity at ambient temperature and pressure. We attribute this performance to a new type of strong binding site for C 2 H 2 . Specifically, halogen⋅⋅⋅HC interactions coupled with other noncovalent in a tight binding site is C 2 H 2 specific versus CO 2 . The binding site is distinct from those found in previous benchmark sorbents, which are based on open metal sites or electrostatic interactions enabled by inorganic fluoro or oxo anions., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Coordination networks that reversibly switch between closed and open phases are of topical interest since their stepped isotherms can offer higher working capacities for gas-storage applications than the related rigid porous coordination networks. To be of practical utility, the pressures at which switching occurs, the gate-opening and gate-closing pressures, must lie between the storage and delivery pressures. Here we study the effect of linker substitution to fine-tune gate-opening and gate-closing pressure. Specifically, three variants of a previously reported pcu-topology MOF, X-pcu-5-Zn, have been prepared: X-pcu-6-Zn, 6=1,2-bis(4-pyridyl)ethane (bpe), X-pcu-7-Zn, 7=1,2-bis(4-pyridyl)acetylene (bpa), and X-pcu-8-Zn, 8=4,4'-azopyridine (apy). Each exhibited switching isotherms but at different gate-opening pressures. The N 2 , CO 2 , C 2 H 2 , and C 2 H 4 adsorption isotherms consistently indicated that the most flexible dipyridyl organic linker, 6, afforded lower gate-opening and gate-closing pressures. This simple design principle enables a rational control of the switching behavior in adsorbent materials., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Two zirconium-organic frameworks were synthesized by exchanging the acetate ligands in [Zr 12 O 8 (OH) 8 (CH 3 COO) 24 ] with polydentate linkers. Partial substitution of acetate groups by a phosphine based linker yielded a new porous framework with this unique dimeric Zr 12 cluster unit as molecular building block. More exhaustive substitution of acetate resulted in cleavage of the Zr 12 unit and formation of UiO-67.

The article presents a comparative analysis of the results of in vivo scanning of oral mucosa leukoplakia with optical coherence tomography (OCT) method and pathological studies in 15 patients (9 females and 6 males aged 27-82). The study revealed specific OCT signs of leukoplakia: even disorder of tissue layering and less clear visualization of lamina propria. OCT is an important stage in the differential diagnosis of leukoplakia of the oral mucosa and significantly complements the clinical and pathomorphological study.

The metal-organic framework [Y(tbpp)]·nDMF (1) was synthesized from yttrium(III) nitrate and the tritopic linker tris(4'-carboxy[1,1'-biphenyl]-4-yl)phosphine (H 3 tbpp). The distance between the coordinating atoms of the carboxylate groups of the extended tridentate phosphine linker is more than 1.8 nm, resulting in an average pore dimension of 0.9 nm in the noninterpenetrated metal-organic framework. The material exhibits high thermal stability and permanent porosity after removal of guest molecules from the one-dimensional pore system. The desolvated compound adsorbs nitrogen, argon, hydrogen, and carbon dioxide. Favorable adsorption of CO 2 over N 2 is predicted using ideal adsorbed solution theory (IAST). The isosteric enthalpies of adsorption of H 2 and CO 2 of -7 and -22 kJ mol -1 , respectively, are representative for metal-organic frameworks with no accessible strong host-guest binding sites, despite the bifunctional nature of the organic ligand. The absence of strong specific adsorption sites was confirmed by in situ powder synchrotron X-ray diffraction of the reversible isobaric CO 2 sorption process. Analysis of the diffraction data indicates that the CO 2 molecules in the pores are disordered and nonlocalized. Despite this, it was possible to quantify the evolution of the occupation of the pores. CO 2 is adsorbed at an approximately constant below 320 K from 10% loading to full capacity at 195 K.

Leukoplakia is one of the most common obligate precancerous lesions of the oral mucosa. leukoplakia treatment is carried out in conjunction with surgery. Removed tissues are sent to pathological examination. The article describes clinical signs and corresponding pathological processes most often revealed by histological study.

In this review the modern wound dressings used in surgical dentistry and maxillofacial surgery are studied. We describe the tupes of wound dressings and their properties. The results of clinical use in various surgical procedures in the oral cavity are presented.

The aim of the study was to elaborate lingual nerve sparing procedure of submandibular gland duct stones extraction. The study involved 43 patients with syalolithiasis treated in Oral Surgery Unit of Central Research Institute of Dentistry and Maxillofacial Surgery in 2013-2015. It was shown that to prevent lingual nerve and artery injury submandibular salivary gland duct should be dissected to the level of obstruction thus allowing adequate visualization of anatomical correlations especially when removing stones from the distal part of the duct.

The article presents data statistics of surgical treatment of leukoplakia by laser ablation for 2014 were examined and operated on 12 patients with verrucous and erosive forms of leukoplakia of the oral mucosa using a diode laser. Only 5 (42%) showed positive results in 7 (58%) patients had recurrent disease, often in the localization of the lesion on the tongue. It is possible that relapse may be associated with incomplete excision of the lesion due to anatomical and morphological features of the oral mucosa in various topographical areas. The study emphasizes the need to find alternative methods of modern surgical excision, one of which can be radiofrequency excision.

Two new, homochiral, porous metal-organic coordination polymers [Zn(2)(ndc){(R)-man}(dmf)]⋅3DMF and [Zn(2)(bpdc){(R)-man}(dmf)]⋅2DMF (ndc=2,6-naphthalenedicarboxylate; bpdc=4,4'-biphenyldicarboxylate; man=mandelate; dmf=N,N'-dimethylformamide) have been synthesized by heating Zn(II) nitrate, H(2)ndc or H(2)bpdc and chiral (R)-mandelic acid (H(2)man) in DMF. The colorless crystals were obtained and their structures were established by single-crystal X-ray diffraction. These isoreticular structures share the same topological features as the previously reported zinc(II) terephthalate lactate [Zn(2)(bdc){(S)-lac}(dmf)]⋅DMF framework, but have larger pores and opposite absolute configuration of the chiral centers. The enhanced pores size results in differing stereoselective sorption properties: the new metal-organic frameworks effectively and stereoselectively (ee up to 62 %) accommodate bulkier guest molecules (alkyl aryl sulfoxides) than the parent [Zn(2)(bdc){(S)-lac}(dmf)]⋅DMF, while the latter demonstrates decent enantioselectivity toward precursor of chiral anticancer drug sulforaphane, CH(3)SO(CH(2))(4)OH. The new homochiral porous metal-organic coordination polymers are capable of catalyzing a highly selective oxidation of bulkier sulfides (2-NaphSMe (2-C(10)H(7)SMe) and PhSCH(2)Ph) that could not be achieved by the smaller-pore [Zn(2)(bdc){(S)-lac}(dmf)]⋅DMF. The sorption of different guest molecules (both R and S isomers) into the chiral pores of [Zn(2)(bdc){(S)-lac}(dmf)]⋅DMF was modeled by using ab initio calculations that provided a qualitative explanation for the observed sorption enantioselectivity. The high stereo-preference is accounted for by the presence of coordinated inner-pore DMF molecule that forms a weak C-H...O bond between the DMF methyl group and the (S)-PhSOCH(3) sulfinyl group.